This invention relates to a solar energy collecting system, particularly an improved light collecting type of solar energy collecting system.
In the prior art, a number of water heating systems for using solar energy have been developed. However, such systems are largely concerned with direct heating types in which a plate having a high coefficient of heat transmission includes a plularity of water tubes exposed directly to the sun rays. However, such systems take too long a time, for example, about 90 minutes, to obtain about 2-3 l of 60.degree. C. water.
Accordingly, to eliminate the shortcomings of the conventional systems, GEM Company in USA had developed U.S. Pat. No. 2,004,200 which is entitled "Parabolic Cup Reflector" and U.S. Pat. No. 4,262,658 which is entitled "Dranable Solar Collector Apparatus" and had recognized officially a superiority of the patents by the Energy Office of U.S. Government and NASA.
However, they have also not completely eliminated such disadvantages of the prior art. As see in FIG. 4, a prior art system consists of a parabolic cup reflector "a" focuses solar energy upon a transparent tube which has a vacuum chamber b formed in its center and a water tube c formed on its external surface. Accordingly, the width "B" of the water tube "c" is wide and, consequently it has the disadvantage of blocking the solar rays which are to be collected for heating action.
Further, the parabolic cup reflector "a" is formed of two concave reflectors so that the overall dimensions thereof are rather large. This prior art apparatus, therefore, does not obtain a maximized light collecting effect, that is, raising the temperature of hot water in a shorter time period in case of cloudy days and the winter season in which available sun time is short.
Furthermore, this prior art system must be installed on a steep ramp, like a roof, so that the space of the structure cannot be used efficiently, a beautiful sight of the structure may be damaged and also it is very difficult to install on a building or upon existing facilities such as apartments.